Over the years, we got a few window related functions and with 2.4 plugins recently we got some more commands. But first take a look on this screenshots showing our layout before and after running plugin functions:

We can hide scrollbars and the toolbar button. Also we can disable close, minimize and maximize buttons on the window title bar. And we disable resizing the window.
I'm not yet sure how to remove the little box on bottom left on Windows. But if you use accounts with privileges set correctly, the user can't go to layout or search mode.
Can you imaging where this is going? I think we can make dialogs in Filemaker with normal layouts.